Devices and methods for facilitating controlled bone growth or repair

ABSTRACT

Bone implantable devices and methodologies permit careful application of biologically active substances and management of bone growth processes. The device includes a body defining a carrier receiving area for locating adjacent bone. Carrier material is located in the carrier receiving area. Substance is delivered onto carrier material through a port. A pathway delivers substance from the carrier receiving area to the bone surface. The body may be in the form of a spinal fusion cage, facet fusion screw, artificial joint, bone fixation plate, interbody graft, IM nail, hip stem, or other bone-to-bone appliances or bone-to-device appliances. In use, carrier is installed in the carrier receiving area of the device. The device is then implanted adjacent a bone. The substance is applied to the carrier for subsequent delivery to the bone. By doping carrier material after device implantation, inadvertent contact of the substance with non-target bone is more easily eliminated.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of co-pending InternationalApplication No. PCT/US02/23262, filed Jul. 23, 2002, which InternationalApplication designates the United States and which itself is acontinuation-in-part of U.S. patent application Ser. No. 09/737,074,filed Dec. 14, 2000, now abandoned, to which priority is claimed.

BACKGROUND OF THE INVENTION

1. Technical Field

This invention is directed generally to devices and methods forfacilitating bone growth, and, in particular, to bone implantabledevices and implantation methodologies that augment beneficial bonegrowth or repair while limiting bone growth in undesirable directions.

2. Background

In orthopedic and neurological surgical procedures it is often importantto facilitate the growth or fusion of bony structures. This may entailgrowth “bone-to-bone” or, depending on the nature of the procedure, boneto device.

Chronic back problems, for example, cause pain and disability for alarge segment of the population. In many cases, such problems areattributable to relative movement between vertebrae in the spine. Spinalsurgery includes procedures to stabilize adjacent vertebrae. Commonstabilization methods often involve fusing adjacent vertebrae together.

Fusion techniques include removing disc material that separates thevertebrae and impacting bone into the disc area. The impacted bone fuseswith the bone material of the two adjacent vertebrae to thereby fuse thevertebrae together.

In a further advance in the art, spinal implants have been developed toincrease the probability of a successful fusion. Such devices generallycomprise a hollow cage into which bone growth inducing substances, suchas bone chips or bone slurry, may be placed. The cage is inserted,either by anterior or posterior approach, into the intervertebral discspace. The cage wall has holes extending radially therethrough,typically throughout the entire cage surface. Bone growth extends intothe device through the radial apertures, facilitating arthrodesisbetween the adjacent vertebral bone structures and allowing for thedecompression of neural elements.

With the continued development of techniques for achieving spinal fusionthrough the use of spine fusion cages, new materials have been developedto augment the fusion process. Traditionally, the patient's own bone, orcadaver bone, was used in the cage to promote bony fusion. Morerecently, powerful new biologic materials have been discovered thatgreatly accelerate the fusion process, in some cases eliminating theneed for donor bone.

However, with the utilization of the newer biologic materials there hasarisen a significant problem. When bone growth inducing agents, such asbone morphogenic proteins (“BMP”), are used in cages of existing designthere is risk of inducing the overgrowth of bone around and intosensitive neural tissues. This is especially the case when a posteriorapproach is utilized to implant a spinal fusion cage, as bony overgrowthtoward the central canal or neural foramen may impinge on spinal nerveroots causing neurological damage. A recent study on posterior lumbarinterbody fusion procedures using rhBMP-2 reported that 58% of patientsexperienced greater than expected bone formation dorsal to the fusioncage. In 30% of the cases, the bony overgrowth compromised the centralcanal, the neural foramen, or both. This study is confirmatory toobservations first made by the present inventor in early 1999.

Typically, the bone growth agent is in liquid form and is applied to anabsorbent carrier material, such as a piece of bovine collagen. Thedoped carrier material is placed with forceps into the interbody space,usually into an open end of the fusion cage after the cage has beenimplanted, but sometimes prior to cage implantation. During placementcarrier material may inadvertently wipe across body areas, includinginternal bony structures, where bone growth is not desired. In addition,as the carrier material is pressed into place agent may squeeze out andflow into adjacent areas. Exacerbating the problem, current protocols donot encourage the use of suction, irrigation and hemostatic agents whenbone growth agent is utilized. Conventional cage design also allows forthe leakage of agent into undesirable areas after implantation throughill-placed apertures in the cage body, in the cage end caps, orotherwise. Because of the powerful stimulatory effects of bone growthagents, uncontrolled application of these substances may lead to seriouscomplications, including severe inflammation, debilitating neuralimpingement, and other potential complications.

Thus, there is a need to better control the bone growth process whenusing a bone implantable device, especially in circumstances wherepowerful bone growth inducing agents are used in conjunction therewith.

In satisfying this need, there is also an opportunity to extend theapplication of bone growth agent based bony fusion to all types of boneimplantable devices to better achieve union of bone-to-bone orbone-to-device, as the case may be.

SUMMARY OF THE INVENTION

In connection with the present invention, there are provided boneimplantable devices and implantation methodologies that allow for thecareful application of bone growth inducing agents, e.g. BMP, andmanagement of bone growth processes.

In accordance with one aspect of the present invention, there isprovided a bone implantable device and carrier combination, whichcombination is implanted into the body prior to application of bonegrowth agent to the carrier. After the device is implanted, the bonegrowth agent may be applied to the carrier in a manner avoiding itscontact with non-target body structures.

In one embodiment the bone implantable device includes a convenientlyplaced injection port that communicates with the carrier material. Afterimplantation of the device bone growth agent is applied to the carriermaterial through the injection port.

In another embodiment, the bone implantable device includes a hollowinterior structure in which carrier material is located. Afterimplantation of the device the bone growth agent is injected into thecarrier material through an injection port. One or more aperturescommunicating with the hollow interior are located on the portion of thedevice that is, upon implantation, adjacent target bone structure,allowing for the controlled delivery of bone growth agent to the targetbone structure.

In still another embodiment, a plenum is provided in the hollow interiorof a bone implantable device to facilitate the even distribution of bonegrowth agent from the injection port into the carrier material.

The bone implantable device may take the form of an interbody spinalfusion cage, a facet fusion screw, an artificial joint, a bone fixationplate, an intervertebral body graft, an IM nail, a hip stem, and otherorthopedic appliances where promoting bone-to-bone growth or growth frombone into the device is beneficial. The bone implantable device itselfis so constructed as to allow the bone growth agent to flow therefromonly in desired directions, i.e. to target bone structures. Manynon-limiting examples are provided herein for illustrative purposes.

As primary examples of device construction for vertebral fusionpurposes, there are provided several embodiments of a fusion cage whichcan be inserted into an intervertebral disc space using either aposterior or anterior approach and which prevents overgrowth of bonearound or into neural tissue. Growth of bone into sensitive areas isprohibited by providing the cage with various zones wherein the cagewall is either perforated or non-perforated. A cage body is providedhaving a posterior end and an anterior end and defining an internalcavity and a longitudinal axis. The cage body has an outer surface and aplurality of apertures extending from the outer surface andcommunicating with the internal cavity in a preselected pattern.Preferably, there is a first non-perforated zone extending from theposterior end of the cage a preselected length toward its anterior end,second and third non-perforated zones on the longitudinal sides, whereinnon-perforated zones are defined by the medial sides of the cageextending in opposing relation from the first zone further toward theanterior end, and two opposed perforated zones oriented so that uponinsertion of the device the perforated zones will be adjacent thevertebral bodies to be fused, which channels the bone growth in asuperior and inferior direction only to allow bone growth across thevertebral interspace. Each end of the cage is provided with anon-perforated closure. Preferably, the posterior end is closedcompletely, while the anterior end may or may not be closed. In thismanner bone growth is prevented in areas adjacent the non-perforatedzones when the fusion cage is in place.

In another example there is provided a novel spine fusion cage whichprovides for the selective occlusion of apertures in the cage wall so asto prevent the growth of bone in undesired directions. As an example,there is provided an inventive cage having outer and inner cageelements. An outer cage body having a posterior end and an anterior enddefines an internal cavity. A plurality of apertures extends through theouter surface of the outer cage body to communicate with the internalcavity in a pattern covering a substantial portion of the outer surfaceof the cage body. An inner cage body is disposed within the internalcavity of the outer cage body and is positioned as to form an annulusbetween the inner wall surface of the outer cage body and the outer wallsurface of the inner cage body. The inner cage body likewise has aplurality of apertures extending through its outer surface so as toestablish communication with the annulus and the outer surface of theouter cage. An end closure means having occluding surfaces suitable forintroduction into the annulus between the outer and inner cages servesto establish one or more desired zones or patterns of occluded aperturesamongst the plurality of apertures in the outer cage body, therebyobstructing bone growth in undesired directions.

In still another example there is provided an end closure means foreffecting the closure of the posterior end of a fusion cage whileestablishing a desired occlusion pattern of apertures in the wall of thefusion cage. The closure means comprises a non-perforated sealing memberto effect the closure of the posterior end of the internal cavity of thefusion cage and one or more occluding surfaces extending from thesealing member essentially parallel to the longitudinal axis of thefusion cage so as to establish one or more desired zones or patterns ofoccluded apertures amongst the plurality of apertures in the cage body.

In still another example, a cage body is provided that has a posteriorend and an anterior end and defines an internal cavity. The cage bodyfurther has an outer surface and a plurality of apertures extendingthrough the outer surface in communication with the internal cavity,wherein the outer surface has a preselected pattern of perforated andnon-perforated zones. A first end closure is secured at a first end ofsaid cage body. A second end closure is provided that has an orificetherein. The second end closure is secured at a second end of the cagebody. At least one of the first end closure and the second end closureis removable so as to provide access to the internal cavity. A plug islocated in the orifice that is capable of being penetrated by a syringeneedle for administering a bone growth agent to said internal cavity.Preferably, a carrier that is compatible with a bone growth or biologicagent and that holds and dispenses the agent in a time released andcontrolled fashion, receives the bone growth agent. By using thisapproach, chances for misapplication of bone growth material are greatlydiminished. A plenum is preferably used to encourage even application ofthe bone growth agent to the carrier material.

Further examples as related to other orthopedic appliances are alsoprovided.

In addition, in accordance with another aspect of the present inventionthere is provided a methodology for implanting bone implantable deviceswherein the device and carrier material are implanted into the body intheir operative positions prior to the loading of bone growth agent intothe carrier material.

In one embodiment, the carrier material is isolated within the boneimplantable device prior to application of the bone growth agent to thecarrier material.

In a preferred embodiment, the bone growth agent is applied to thecarrier material via an injection port.

In another preferred embodiment, bone growth agent is applied to thecarrier material through a plenum communicating with an injection port.

A better understanding of the present invention, its several aspects,and its advantages will become apparent to those skilled in the art fromthe following detailed description, taken in conjunction with theattached drawings, wherein there is shown and described the preferredembodiments of the invention, simply by way of illustration of the bestmode contemplated for carrying out the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 anatomically illustrates a bilateral posterior insertion of twoinventive spine fusion cages to achieve fusion across the L5/S1 discspace.

FIG. 2 is an exploded perspective view of an embodiment of an inventivecage having preselected perforated and non-perforated zones on its outersurface.

FIG. 3 is a perspective view taken along line 3-3 of FIG. 2.

FIG. 4 is a sectional view taken along line 4-4 of FIG. 2.

FIG. 5 is perspective view of an embodiment of an inventive cage havingouter and inner cage elements.

FIG. 6 is a sectional view taken along line 6-6 of FIG. 5.

FIG. 7 is a perspective view of an end closure for use in connectionwith the cage of FIG. 5.

FIG. 8 is a top sectional view of the cage of FIG. 5 including the endclosure of FIG. 7.

FIG. 9 is an exploded side view of a conventional fusion cage modifiedto utilize an inventive end closure means to selectively occlude certainapertures in the outer surface of the cage.

FIG. 10 depicts the partial insertion of the inventive closure meansinto the cage of FIG. 9.

FIG. 11 depicts the full insertion of the inventive closure means intothe cage of FIG. 9.

FIG. 12 is top sectional view of a modified conventional cage includingan inventive end closure means.

FIG. 13 is an exploded perspective view of an embodiment of an inventivecage having an end cap and an injection port.

FIG. 14 is a partial cross-sectional view of an embodiment of a boneimplantable device shown located within a bone structure.

FIG. 15 is a cross-sectional view of an embodiment of a bone implantablestructure shown functioning as a ball portion of a ball and socketjoint.

FIG. 16 is a cross-sectional view of the embodiment of FIG. 15 takenalong line 16-16 of FIG. 15.

FIG. 17 is a side view of an artificial joint fused to adjacentvertebrae.

FIG. 18 is a cross-sectional view taken along lines 18-18 of FIG. 17.

FIG. 19 is a partial cross-sectional view of a bone implantablestructure for use as a spinal fusion cage wherein the spinal fusion cagehas a plenum member located therein.

FIG. 20 is a perspective view of the plenum member of FIG. 19.

FIG. 21 is a cross-sectional view taken along line 21-21 of FIG. 19.

FIG. 22 is a perspective view of a bone implantable structure for use asan intervertebral body graft.

FIG. 23 is a top view of the intervertebral body graft of FIG. 22.

FIG. 24 is a cross-sectional view of the intervertebral body graft ofFIG. 22.

FIG. 25 is a side view of a bone implantable structure located on a bonestructure.

FIG. 26 is a top view of the bone implantable structure of FIG. 25.

FIG. 27 is an enlarged perspective view of the bone implantablestructure of FIG. 27.

FIG. 28 is a perspective view of another embodiment of the spinal fusioncage.

FIG. 29 is a partial cross-sectional view of a “360° fusion” vertebralfusion including the spinal fusion cage of FIG. 19 and a facet fusionscrew engaging adjacent vertebral facets.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Before explaining the present invention in detail, it is important tounderstand that the invention is not limited in its application to thedetails of the construction illustrated and the steps described herein.The invention is capable of other embodiments and of being practiced orcarried out in a variety of ways. It is to be understood that thephraseology and terminology employed herein is for the purpose ofdescription and not of limitation.

As used herein the phrases “bone growth inducing agent(s),” “bone growthagent(s),” “bone growth accelerant”, “bone morphogenic protein(s),” and“BMP” refer synonymously to any substance useful in stimulating bonegrowth, whether a protein or not. Such substances are well known in theart.

As used herein the terms “carrier” and “carrier material” refersynonymously to any material capable of absorbing or otherwise holdingor containing a bone growth inducing agent and which allows for thedelivery of such agent to a target bone structure.

In the preferred embodiment of the present invention, a bone implantabledevice and carrier combination is implanted into the body prior toapplication of bone growth agent to the carrier. As indicated in thevarious example embodiments disclosed herein, the device may take avariety of forms. Typically, the device is made from titanium, alloys oftitanium, Carbon fiber, bone or ceramic, but it may be made of anysuitably strong material tolerated by the body. The device may comprisea unitary structure or may be of a multi-piece construction. In certainapplications it may be advantageous to include a removable end cap orcover to allow access to the interior of the device. Further, the deviceor portions of the device, such as an end cap or other component may beconstructed of a bio-absorbable material.

The device is preferably pre-loaded with carrier material, which may beretained in a hollow within the device or otherwise retained, such asadhesively, to an outside surface portion of the device. After thedevice and carrier combination is implanted, bone growth agent isapplied to the carrier in a manner avoiding its contact with non-targetbody structures.

As bone growth agent is conventionally applied in liquid form, severalpreferred embodiments of the bone implantable device include aconveniently placed injection port that communicates with the carriermaterial. A plenum may be used to confine the flow of the bone growthagent from the injection port to the carrier material and to obtain evensaturation of the material.

Besides enabling the better handling of the bone growth agent during thesurgical procedure, the inventive bone implantable device better managesthe stimulated bone growth by providing, in effect, one or moreartificial tissue planes that prevent bony overgrowth in undesirabledirections. The device allows bone growth agent to elute to the targetbone structure, preferably through pathways or openings directlycontacting the target bone structure, but the bone growth agent isotherwise confined in the device. The device walls prevent leakage ofthe bone growth agent toward sensitive areas or structures.

Bone implantable devices and implantation methodologies of the inventionallow for the careful application of biologically active substances,such as bone growth accelerants including bone morphogenic proteins(BMP) for management of bone growth processes. Although bone growthaccelerants are referred to in the below examples, it should beunderstood that the bone implantable devices of the invention may beused to deliver other biologically active substances as well. As will bediscussed below, the bone implantable device of the invention may takethe form of interbody spinal fusion cages, facet fusion screws,artificial joints, bone fixation plates, interbody grafts, e.g.intervertebral body grafts, IM nails, hip stems, and other orthopedicappliances where promoting bone-to-bone growth or growth from bone intothe device is beneficial. Additionally, it is contemplated that the boneimplantable devices of the invention may be used to deliver substancesto enhance the growth of cartilage, tendon and other body structures inaddition to bone.

The present invention will be further understood with reference to thefollowing non-limiting examples.

EXAMPLE 1 Spine Fusion Cages

Several types of conventional spine fusion cages have been designed,such as those described by Bagby, Brantigan and Ray, respectively, inAthrodesis by the Distraction-Compression Method Using a Stainless SteelImplant, Orthopaedics 1988, Vol. 11:931-4; A Carbon Fibre Implant to AidInterbody Lumbar Fusion, Spine 1991, 16 (Suppl):S277-82 (with Steffeeand Geiger); and Threaded Titanium Cages for Lumbar Interbody Fusions,Spine 1997, 22:667-80; and as described in the patent art, for example,in U.S. Pat. Nos. 4,501,269; 5,055,104; 5,571,192; 5,702,449; 5,876,457;5,906,616; 5,976,187; 5,980,522; 6,010,502; 6,015,436; and 6,039,762.Each of the foregoing publications and patents is incorporated herein byreference.

Such devices provide for a relatively simple and effective technique forimplementing lumbar interbody fusion by correcting any existingmechanical deformity of the spine while providing stability and a goodenvironment until successful arthrodesis is obtained. These cage devicesare hollow and are positioned between the articulating vertebrae, wherethey support and immobilize the joint as well as contain the growth ofthe bone graft that is packed into the internal cavity of the device.

Anterior lumbar interbody fusion (ALIF) and posterior lumbar interbodyfusion (PLIF) are two commonly adopted approaches for grafted lumbarinterbody fusion with augmentation via a spine fusion cage. ALIF isperformed through a retroperitoneal or transperitoneal approach withextensive discectomy followed by the placement of one or more cages inthe vertebral interspace. In PLIF, partial or complete laminectomy andfacetectomy is followed by posterior discectomy and the placement of oneor more cages in the vertebral interspace. FIG. 1 is illustrative of abilateral posterior insertion of two inventive spine fusion cages 20 toachieve fusion across the L5/S1 disc space. The cages 20 are secured farenough apart from each other (by a few millimeters) to avoid contact andpotential back-threading. It should be understood that the fusion cagesof this invention can be installed in their operative positions viaeither the anterior or posterior approaches; however, the posteriorapproach is the most dangerous in regards for bony overgrowth impingingon neural tissue particularly when the cage is used along with bonegrowth inducing materials.

The inventive cages 20 promote bony fusion by holding adjacent levelsimmobile and by allowing bone to grow only into the vertebral bodies anaway from the spinal canal and nerve roots. Designs that do not controldirection of growth are undesirable for use with biologic bone growthagents to the extent unchecked bony overgrowth may impinge upon neuraltissues. Through the present invention there are provided designs forspine fusion cages which prevent bone growth around and into sensitiveareas of neural tissue.

Referring now to FIGS. 2-4, and in accordance with one embodiment of thepresent invention, there is provided an inventive spine fusion cage 20wherein growth of bone into sensitive areas is prohibited by providingthe cage with various zones or areas wherein the cage wall is eitherperforated or non-perforated. A cage body 22 is provided having aposterior end 24 and an anterior end 26 and defining an internal cavity28 and a longitudinal axis 30. The cage body 22 is typically between20-25 mm in length and may be of a variety of diameters, dimensions andheights. The cage body 22 has an outer surface 32 and a plurality ofradial apertures 34 or pathways extending through the outer surface 32in communication with the internal cavity 28 in a preselected pattern.Preferably, there is a first non-perforated zone 36 extending from theposterior end 24 of the cage body 22 a preselected length, preferably5-10 mm, toward its anterior end 26, second and third non-perforatedzones 38, 40 on the lateral sides of the cage body 22 extending inopposing relation from the first zone 36 further toward the anterior end26, and two opposed perforated zones 42, 44 oriented cephalad (or to thesuperior side) and caudad (or to the inferior side) so that uponinsertion of the device the perforated zones 42, 44 will be adjacent thevertebral bodies to be fused to allow bone growth across the vertebralinterspace. Ends 24, 26 of the cage body 22 are provided with anon-perforated closure. In the illustrated embodiment, the anterior end26 is closed by an integral non-perforated end wall 46, while there isprovided a removable end cap 48 securable, by threaded attachment,friction fit or otherwise, to the posterior end 24 of the cage body 22.The end cap 48 may be provided with a recess 50 for receiving aninsertion tool, for example if the end cap is made to threadably connectto the cage body, and there is preferably provided on the top of the endcap 48 a line score 52 for aiding proper orientation of the device inthe vertebral interspace.

The cage body 22 may be provided with threads 54, projections, ridges,protrusions, barbs, spurs or other insertion means to aid in placementof the cage within the interbody area. The anterior end 26 can berounded in order to facilitate the insertion of the cage 20 relative toone or more bone structures. The cage 20 may be made of surgical steel,titanium or other acceptable implantable materials. Typically, the cage20 is countersunk into the vertebral interspace with the end cap 48 inplace by using an insertion tool (not shown) to screw the cage 20 intoposition. Once the cage is properly aligned, the end cap 48 is removedso that bone growth inducing material can be packed into the internalcavity 28 of the cage body 22, whereupon the end cap 48 is tightlyreplaced.

As can now be appreciated, the inventive cage 20 prevents bone growthinto areas adjacent the non-perforated zones when the fusion cage is inplace. Because the posterior 5-10 mm of the cage is non-perforated,including, importantly, the end cap, bony overgrowth is inhibited inareas immediately adjacent the posteriorly located neural tissues. Insimilar fashion, lateral overgrowth of bone is impeded by the second andthird non-perforated zones. Desired growth through the vertebralinterspace, however, is facilitated via the perforated zones.

It should be understood to be within the ordinary skill of one in theart to modify the placement of the various perforated and non-perforatedzones as warranted by orthopaedic considerations to achieve desired bonegrowth and preclude unwanted bone growth. It is also within the ordinaryskill of one in the art to modify the aforedescribed device for anteriorinsertion procedures by providing a removable end cap on the anteriorend of the cage body and reversing the thread direction on the outsidesurface of the cage body.

As mentioned above, it is also advantageous for a surgeon to have theability to selectively occlude apertures in the cage wall to preventbone growth in undesired directions. Now referring to FIGS. 5-8, toachieve this object, and in accordance with another embodiment of thepresent invention, there is provided a spine fusion cage 120 having anouter cage body 122 with a posterior end 124 and an anterior end 126 anddefining an internal cavity 128 and a longitudinal axis 130. The outercage body 122 has an outer surface 132 and a plurality of radialapertures 134 extending through the outer surface 132 in communicationwith the internal cavity 128 in a pattern covering a substantial portionof the outer surface 132 of the cage body 122. An inner cage body 136into which is placed bone growth inducing substances is disposed withinthe internal cavity 128 of the outer cage body 122 and is positioned asto form an annulus 138 between the inner wall surface 140 of the outercage body 122 and the outer wall surface 142 of the inner cage body 136.The inner cage body 136 likewise has a plurality of radial apertures 144extending through its outer surface 142 so as to establish communicationwith the annulus 138 and the outer surface 132 of the outer cage body122. A solid end closure 146 having opposed occluding surfaces 148, 150suitable for introduction into the annulus 138 serves to establish oneor more desired zones or patterns of occluded apertures amongst theplurality of apertures in the outer cage body 122, thereby obstructingbone growth in undesired directions.

More specifically, as shown in FIG. 7 end closure 146 is comprised of anon-perforated cap or closure means 152 having occluding surfaces 148and 150 extending therefrom. Such surfaces may be of sufficient lengthto extend to the bottom of the cage member 120 as shown in FIG. 5 or maybe of a more limited length so as to occlude only a portion of theapertures 134 in the outer cage body 122. The end closure 146 may beconstructed so as to provide a top circumferential crown portion 154 andbetween the occluding surfaces 148, 150 a shoulder 156 which may engagea rib means 158, 160 as shown in FIG. 8 to act as a longitudinal stopand to limit the degree of rotation which can be made by occludingsurfaces 148, 150 so as to maintain the selected occlusion pattern. Whenpositioned within the annulus 138 of the fusion cage 120, the occludingsurfaces 148, 150 serve to close openings in the posterior end of thecage 120 as well as to occlude openings or pathways which are in alateral position so as to effect bone growth through the apertures inthe caudal and cephalad directions when placed in the desired positionbetween two vertebrae. Various interchangeable forms of end closures maybe provided, for example having differently shaped and dimensionedoccluding surfaces, so as to provide for the surgeon a selection whichmeets objectives according to various orthopaedic exigencies. It is alsowithin the scope of this invention that the shape and dimensions of theoccluding surfaces may be modifiable by the surgeon, such as if theoccluding surfaces comprise a surgical plastic adapted to be cut ortrimmed to achieve a desired configuration. In this manner, a cagepossessing a full pattern of apertures can be used as a “universal” cagein combination with one of a wide selection of end closures or amodifiable end closure to achieve any desired patterned of perforation.

The end closure 146 can be threaded or otherwise designed to effect theclosure of the posterior end of the cage 120 and may be provided withsecuring means such as square or hex-shaped recess 162 which can be usedwith a socket wrench to tightly position the end closure 146 in theposterior end of the fusion cage 120. In complementary fashion, threadsmay be provided at the posterior end of the cage 120 to receive athreaded end closure 146 or it can be so adapted that the end closure146, when not threaded, can be simply snapped into place to effect thedesired closing of the fusion cage 120.

A thread 164 may be provided as part of the outer surface 132 of thefusion cage 120. Such a thread can be replaced with a plurality ofdiscrete threads or a plurality of projections, ridges, protrusions,barbs or spurs and be within the spirit and scope of the invention.

In assembly of the fusion cage of this embodiment of the invention,following introduction of the selected biologic material into theinternal cavity 128 within the inner cage body 136, the annulus 138remains clear so as to easily accept end closure 146 within the annulus138 while the biologic materials are retained in the internal cavity128. Through the dimensioning, shaping and rotation of occludingsurfaces 148, 150 there is achieved an occlusion of apertures so as todefine the desired pattern of apertures through which bone growth is tobe permitted.

In keeping with the teachings of the present invention, there is furtherprovided a novel closure for conventional spine fusion cages which canbe used with little or no modification to presently available fusioncages in preventing bone growth into undesirable areas. This embodimentinvolves providing a means for the occlusion of selected apertures incurrently available fusion cages, such as to those commonly referred toas Brantigan, BAK and Ray cages, so that bone growth is directed onlytoward the vertebral bodies and away from the spinal canal and nerveroots.

Making reference now to FIGS. 9-11, there is illustrated an end closure220 for effecting the closure of the posterior end 222 of a conventionalfusion cage body 224 while establishing a desired occlusion pattern ofapertures in the wall of the cage body 224, which cage possessesapertures 226 substantially entirely thereabout. The end closure 220comprises a non-perforated sealing member 228 to effect the closure ofthe posterior end 222 of the cage body 224 and one or more occludingsurfaces 230, 231 extending from the sealing member 228 essentiallyparallel to the longitudinal axis 230 of the cage body 224 so as toestablish one or more desired zones or patterns of occluded aperturesamongst the plurality of apertures in the cage body 224. Reference ismade to the disclosure provided above with respect to the aforedescribedend closure 146, which disclosure is equally applicable to end closure220 and further recitation is believed unnecessary. Suffice it to saythat the prior described end closure 146 may be made adaptable toconventional fusion cages so as to achieve the objectives of the presentinvention.

As depicted in FIG. 12, if desired the conventional type of fusion cagecan be so modified as to provide ribs 232, 234 in association with theinner surface of the posterior end of the cage according to theteachings herein. FIG. 12 provides a top view of the fusion cage of FIG.11 along the line 12-12 which shows the placement of the ribs 232 and234 to accommodate occluding surfaces 230, 231 of the end closure 220.

Referring now to FIG. 13, an exploded view of an embodiment of aninventive cage 300 is shown having an end cap 302 and an end cap 304having an orifice 306. Orifice 306 is preferably sealed with a plug 308,e.g. a silicone plug or a plug of another material capable of beingpenetrated by a syringe needle to dope a carrier 310. Carrier 310 isprovided to receive bone growth accelerants, such as bone morphogenicproteins, and is located in the interior of cage 300. A preferredcarrier 310 is a sponge type material such as bovine collagen sponge orany type of collagen that will bind to bone growth accelerant. In use,the cage 300 is desirable because cage 300 may be located within apatient prior to loading cage 300 with bone growth accelerants. Locatingcage 300 prior to loading the bone growth accelerant prevents bonegrowth accelerant from inadvertently contacting areas of the patientthat are not intended to experience bone growth. After the cage 300 islocated, bone growth accelerant may be carefully administered via asyringe needle, which is pushed through plug 308. Once the syringeneedle has penetrated plug 308, bone growth accelerant may be deliveredto the carrier 310, e.g. sponge material. By doping the carrier material310 in this way, the risks associated with locating a cage 300 filledwith bone growth accelerant are minimized. Additionally, the bone growthaccelerant may be pre-loaded onto the carrier material 310 in adissolvable form, e.g., a crystalline form, gel or other form that willeventually migrate outside of cage 300 once implanted into a human bodyand exposed to body fluids, body heat, etc. Of course, a dissolvableform of carrier material may be utilized in any of the examples of theinvention as desired.

Referring now to FIG. 28 a partial cross-sectional view of a rectangularembodiment of an inventive cage 350 is shown having a first end 352 anda second end 354. Second end 354 defines an orifice 356. Splines 358 areprovided to assist in securing cage 350 in a desired location. Orifice356 is preferably sealed with a plug, e.g. a silicone plug or a plug ofanother material capable of being penetrated by a syringe needle to dopea carrier material 360. Holes 361 are used to manipulate cage 350 duringplacement of cage 350. Carrier 360 is provided to receive bone growthaccelerants, such as bone morphogenic proteins, and is located in theinterior of cage 350. A preferred carrier 360 is a sponge type materialsuch as bovine collagen sponge or any type of collagen that will bind tobone growth accelerant. In use, the cage 350 may be located within apatient prior to loading cage 350 with bone growth accelerants. Locatingcage 350 prior to loading the bone growth accelerant prevents bonegrowth accelerant from inadvertently contacting areas of the patientthat are not intended to experience growth. After the cage 350 islocated, bone growth accelerant may be carefully administered throughorifice 356. Preferably, bone growth accelerant is delivered via asyringe needle, which is pushed through a plug located within orifice356. Once the syringe needle has penetrated the plug, bone growthaccelerant may be delivered to the carrier 360, e.g. sponge material. Bydoping the carrier material 360 in this way, the risks associated withlocating a cage 350 filled with bone growth accelerant are minimized.Additionally, bone growth accelerant may be pre-loaded onto the carriermaterial 360 in a dissolvable form, e.g., a crystalline form, gel orother form that will eventually migrate outside of cage 350 onceimplanted into a human body and exposed to body fluids, body heat, etc.Bone growth accelerant passes through pathways or orifices 370 tocontact target bone material.

As a further example of a bone implantable device of the invention, anexploded view of an embodiment of an inventive cage 400 is shown inFIGS. 19 and 21 having an end cap 404 defining an orifice. The orificeis preferably sealed with a plug 408, e.g. a silicone plug or a plug ofanother material capable of being penetrated by a syringe needle. Acarrier 410 for a bone growth accelerant, such as bone morphogenicprotein, is located in the interior of cage 400. A preferred carrier 410is compatible with a bone growth or biologic agent and holds anddispenses the agent in a time released and controlled fashion. Anexample of a suitable carrier 410 is a bovine collagen material. In use,the cage 400 may be located within a patient prior to loading cage 400with bone growth accelerants. Placement of cage 400, e.g., betweenadjacent vertebra as shown in FIG. 29, prior to loading the bone growthaccelerant prevents bone growth accelerant from inadvertently contactingareas of the patient that are not intended to experience bone growth.After the cage 400 is located, bone growth accelerant may be carefullyadministered through the orifice defined by end cap 404. A preferredmethod is via a syringe needle, which is pushed through plug 408. Oncethe syringe needle has penetrated plug 408, bone growth accelerant maybe delivered into plenum 409, which assists in evenly distributing thebone growth accelerant to the carrier 410, i.e., assists in dopingcarrier 410. As shown in FIGS. 19 and 20, plenum 409 is provided with aplurality of pathways or orifices 411 though which the bone growthaccelerant may migrate into carrier 410. Preferably, orifices 411 aredistributed over the length of plenum 409 such that a greaterconcentration of orifices may be found on an end of the plenum oppositeplug 408. The unequal distribution of orifices 411 over the length ofplenum 409 is designed to compensate for a disparity in the amount ofbone growth accelerant delivered into the plenum 409. Alternatively,orifices 411 may be smaller at one end and larger at an end of theplenum 409 opposite plug 408. In either case, an orifice area near anend of the plenum 409 opposite plug 408 is preferably greater than anorifice area on plenum 409 nears plug 408. The desired result is for thebone growth accelerant to migrate into carrier 410 in a uniformdistribution over the length of carrier 410.

Referring now to FIG. 29, a transarticular screw, such as facet fusionscrew 420 is shown as yet another example of a bone implantable deviceof the invention. Facet fusion screw 420 is constructed of body 422,which defines a carrier receiving area 424. An end cap may be providedto seal the carrier receiving area, such as upper end cap 426. Upper endcap 426 is preferably provided with an injection port 428 to facilitatedelivery of bone growth accelerant onto a carrier material for dopingthe carrier material that has been located within the carrier receivingarea 424. Pathways or orifices 430 are provided in a location adjacentto vertebral facets 552 a. Bone growth accelerant located within thecarrier receiving 424 area migrates outwardly through pathways 430 intocontact with adjacent vertebral facets 552 a and promotes bone growththrough pathways 430 to secure facet fusion screw 420 to the vertebrae,thereby immobilizing adjacent vertebrae with respect to one another.Facet fusion screw 420 is shown being used in combination with spinalfusion cage 400 discussed above, to achieve a “360° fusion” of adjacentvertebrae 552. Although facet fusion screw is shown being used withspinal fusion cage 400, use of facet fusion screw 420 with other spinalfusion cages is also contemplated.

In addition to the interbody spinal fusions cages discussed above,further embodiments of applicant's bone implantable device invention maytake the form of a an IM nail 450 (FIG. 14), hip stem 500 (FIGS. 15,16), artificial disk assembly 550 (FIGS. 17, 18), interbody graft 650(FIGS. 22-24), bone fixation plates 700 (FIGS. 25-27), and otherorthopedic appliances where promoting bone-to-bone growth or growth frombone into the device is beneficial.

EXAMPLE 2 IM Nails

Referring now to FIG. 14, IM nail 450 is shown located in an interiorcavity of femur 452. Femur 452 is shown with break 453. IM nail 450 hasa body 451 and an end cap 454 that encloses carrier receiving area 456.Without end cap 454, a port is accessible for doping carrier materiallocated in carrier receiving area 456. A plurality of pathways ororifices 458 communicates carrier receiving area 456 with an exterior ofbody 451. Preferably, IM stem 450 is carefully selected so that, uponplacement within femur 452, orifices 458 are located adjacent break 453.By loading carrier receiving area 456 with a carrier and bone growthagent and locating orifices 458 adjacent break 453, improved mending ofbreak 453 is facilitated.

EXAMPLE 3 Hip Stems

Additionally, the bone implantable device of the invention may befashioned into hip stem 500 (FIGS. 15, 16). Hip stem 500 is shownlocated in one end of a femur 501. Hip stem 500 has a body 502 defininga carrier receiving area 504 and a ball joint 505. Preferably, carrierreceiving area 504 is accessible via end cap 506. End cap 506 isprovided with injection port plug 508 for doping the carrier material.Carrier receiving area 504 is provided to receive a carrier 503 for bonegrowth agent. Pathways or orifices 510 allow bone growth agent tomigrate from carrier receiving area 504 to an outside surface of body502. Additionally, bone growth will propagate through orifices 510 toassist in securing hip stem 500 within femur 501.

EXAMPLE 4 Artificial Disks

Referring back to FIGS. 17 and 18, an artificial disk assembly 550 isshown between two adjacent vertebrae 552. Artificial disk assembly 550includes an upper disk member 554 having a concave lower surface 556 anda perforated upper surface 558. Perforated upper surface 558 has aplurality of pathways or orifices 560 formed therein. Preferably, upperdisk member 554 defines a carrier receiving area 562. Carrier receivingarea 562 is accessible via a cap member 564. Preferably, cap member 564is provided with an injection port plug to facilitate doping of carriermaterial. Artificial disk assembly 550 additionally includes lower diskmember 568 having a concave upper surface 570 and a perforated lowersurface 572. Perforated lower surface 572 has a plurality of pathways ororifices 574 (FIG. 18) formed therein. Preferably, lower disk member 568defines a carrier receiving area 576. Carrier receiving area 576 isaccessible via a cap member 578, which preferably receives an injectionport plug 579 (FIG. 18) through which the carrier material may be doped.Concave surfaces 556 and 570 slidingly engage curved surfaces ofartificial spinal disk 580, which is preferably constructed of a polymeror other suitable material. Perforated surfaces 558 and 572 are locatedadjacent respective vertebrae 552. Once a bone growth accelerant isinjected onto carrier material located within carrier receiving areas562 and 576, or as pre-loaded dissolvable carrier material is dissolved,the bone growth accelerant migrates into contact with vertebrae 552.Bone material is then stimulated to grow through orifices 560 and 574 tosecure the upper disk member 554 and lower disk member 568 to adjacentvertebrae 552.

EXAMPLE 5 Interbody Grafts

As a further example of a bone implantable device, an interbody graft650 is shown in FIGS. 22-24. Interbody graft 650 may be inserted betweenadjacent vertebrae to facilitate fusion of the vertebrae. Interbodygraft 650 is constructed of a ring shaped body defining an inner surface651 and an annular carrier receiving area 652 for receiving carriermaterial 654. Cap 656 is provided to access carrier receiving area 652.Preferably, cap 656 is provided with an injection port 658 forfacilitating doping carrier material 654, i.e., for facilitatingdelivery of bone growth accelerant material onto carrier material 654. Aplurality of pathways or orifices 660 are provided on inner surface 651for delivery of bone growth accelerant to adjacent bone material. As thebone growth accelerant passes through orifices 660, adjacent bonestructures are stimulated to grow into the opening defined by innersurface 651 where the two vertebrae fuse to one another.

EXAMPLE 6 Bone Fixation Plates

As shown in FIGS. 25-27, a bone fixation plate 700 is another example ofa bone implantable device of the invention. Bone fixation plate 700 maybe used to assist in mending broken bones, such a collar bone 701. Bonefixation plate 700 is provided with screw orifices 702 for receivingscrews 704. Screws 704 are used to affix bone fixation plate 700 to bone701. Bone fixation plate 700 defines a carrier receiving area 706, whichmay be a hollow area within bone fixation plate 700 or may be a recessedarea defined by bone fixation plate 700 as shown most clearly in FIG.27. Carrier receiving area 706 is provided to receive carrier material708 (FIG. 25) and to position carrier material 708 adjacent a desiredbone structure. In this embodiment, carrier receiving area 706 alsofunctions as a pathway to facilitate the delivery of bone growthaccelerant to the bone structure. An injection port 712 may be providedto access carrier receiving area 706 so that bone growth accelerant maybe carefully administered to the carrier after implantation of bonefixation plate 700, i.e., so that the carrier material 708 can be doped.

In each of the above described examples, a conveniently placed injectionport provides the ability to deliver bone growth accelerant in a mannerthat reduces potential contact with non-target bone structures. Theinjection port is preferably located on the device body and communicateswith a carrier material located in the carrier receiving area. Theinjection port facilitates delivery of bone growth accelerant to thecarrier after implantation of the device. Alternatively, avoidinginadvertent contact with non-target bone structures may be achieved ineach of the above examples by pre-loading devices with a dissolvableform of bone growth accelerant that liquefies after exposure to animplanted environment.

Preferably, the bone implantable device includes a carrier receivingarea that may be a hollow interior structure in which carrier materialis located. When utilizing an injection port, bone growth accelerant isinjected into the carrier material through an injection port afterimplantation of the device. One or more apertures communicating with thecarrier receiving area may be located on a portion of the device thatis, upon implantation, adjacent target bone structure, which allows forcontrolled delivery of bone growth accelerant to the target bonestructure. A plenum may be provided in the carrier receiving area in aninterior of the bone implantable device to facilitate the evendistribution of bone growth accelerant from the injection port into thecarrier material.

While the discussion has focused primarily on methods and devices foraccelerating bone growth, it is contemplated that the devices andmethods of the invention may also be used to deliver agents to otherbody structures including tendons and ligaments.

Finally, although the facet type screws discussed herein are shownfacilitating the fusion of vertebral facets, it should be understoodthat the screws discussed herein may be useable in other ways and tofuse other bone structures besides vertebral facet structures discussedherein.

While the invention has been described with a certain degree ofparticularity, it is understood that the invention is not limited to theembodiment(s) set for herein for purposes of exemplification, but is tobe limited only by the scope of the attached claim or claims, includingthe full range of equivalency to which each element thereof is entitled.

1. An interbody spine fusion cage for fusing adjacent vertebrae, saidspinal fusion cage comprising: a cage body defining an outside surface;a carrier receiving area defined by said cage body; an un-doped carriermaterial loaded in said carrier receiving area; a port that communicatessaid outside surface with said carrier receiving area for facilitatingdelivery of a biologically active substance onto said un-doped carriermaterial; a pathway that communicates with said carrier receiving areafor delivering said biologically active substance from said carrierreceiving area to a target bone structure; an end cap on an end of saidcage body for enclosing said carrier receiving area; wherein said portis located in said end cap; and further comprising: a plug in said portadapted to be penetrated by a delivery device.
 2. An interbody spinefusion cage according to claim 1 wherein: said delivery device is asyringe.
 3. An implantable device for locating within a body, saidimplantable device comprising: a body defining an outside surface; acarrier receiving area defined by said body; an un-doped carriermaterial loaded in said carrier receiving area; a port that communicatessaid outside surface with said carrier receiving area for facilitatingdelivery of a biologically active substance onto said un-doped carriermaterial; a pathway that communicates with said carrier receiving areafor delivering said biologically active substance from said carrierreceiving area to a target bone structure; a plug in said port adaptedto be penetrated by a syringe; and the interbody spine fusion cagefurther comprising: a substantially solid end cap on an end of said cagebody wherein said end cap encloses said carrier receiving area; andwherein said port is located in said end cap.
 4. An interbody spinefusion cage for fusing adjacent vertebrae, said spinal fusion cagecomprising: a cage body defining an outside surface; a carrier receivingarea defined by said cage body; an un-doped collagen carrier materialloaded in said carrier receiving area; a port that communicates saidoutside surface with said carrier receiving area for facilitatingdelivery of a biologically active substance onto said un-doped carriermaterial; a pathway that communicates with said carrier receiving areafor delivering said biologically active substance from said carrierreceiving area to a target bone structure; a plug in said port adaptedto be penetrated by a syringe; a substantially solid end cap on an endof said cage body wherein said end cap encloses said carrier receivingarea; and wherein said port is located in said end cap.
 5. Animplantable device for locating within a body, said implantable devicecomprising: a body defining an outside surface; a carrier receiving areadefined by said body; an un-doped collagen carrier material loaded insaid carrier receiving area; a port that communicates said outsidesurface with said carrier receiving area for facilitating delivery of abiologically active substance onto said un-doped carrier material; apathway that communicates with said carrier receiving area fordelivering said biologically active substance from said carrierreceiving area to a target bone structure; a plug in said port adaptedto be penetrated by a syringe; a substantially solid end cap on an endof said cage body wherein said end cap encloses said carrier receivingarea; and wherein said port is located in said end cap.
 6. A boneimplantable device for locating adjacent a target bone structure, saidbone implantable device comprising: a body defining an outside surface;a carrier receiving area defined by said body; a pre-loaded collagencarrier material in said carrier receiving area, said pre-loadedcollagen carrier material comprising a biologically active substance; apathway that communicates with said carrier receiving area fordelivering said biologically active substance from said carrierreceiving area to the target bone structure; the interbody spine fusioncage further comprising: a substantially solid end cap on an end of saidcage body wherein said end cap encloses said carrier receiving area; andwherein a port is located in said end cap; a plug in said port, saidplug adapted to be penetrated by a syringe.
 7. A bone implantable devicefor locating adjacent a target bone structure, said bone implantabledevice comprising: a body defining an outside surface; a carrierreceiving area defined by said body; a pre-loaded sponge material insaid carrier receiving area, said pre-loaded sponge material comprisinga biologically active substance; a pathway that communicates with saidcarrier receiving area for delivering said biologically active substancefrom said carrier receiving area to the target bone structure; theinterbody spine fusion cage further comprising: a substantially solidend cap on an end of said cage body wherein said end cap encloses saidcarrier receiving area; and wherein a port is located in said end cap; aplug in said port, said plug adapted to be penetrated by a syringe.